1. Field of the Invention
The present invention relates generally to rotary valves and, more particularly, to an improved valve stem assembly.
2. Description of the Background
Larger diameter rotary valves, such as ball valves and plug valves, may typically utilize trunnions to secure the rotary element within the valve body. In other words, the rotary element is trunnion mounted. As an alternative to trunnion mounting of the rotary element, smaller valves may allow the rotary element to float within the valve body. In these smaller valves, an enlarged end may then be provided on the valve stem to retain the valve stem within the valve body. The enlarged end of the valve stem secures the valve stem in the valve body making the stem virtually blow out proof. However, for trunnion mounted rotary elements, the enlarged end cannot be used because the valve stem and rotary element cannot be inserted into the body due to the presence of the trunnions.
Therefore, in valves used in the last several decades, the trunnion mounted rotary elements utilize an external plate to secure the valve stem to the valve body. The plate is bolted onto the valve body. The valve stem may then have an enlarged end, which is larger than the opening in the plate bolted onto the valve but is not larger than the opening in the rotary valve through which the stem is used to engage and rotate the rotary element.
However in this type of valve, which has been used for decades, forces produced by the actuator by repeatedly opening and closing the valves may cause the bolts holding the plate to the body to fatigue whereupon there is a potential that the valve stem may be released from the valve when the valve is under pressure.
The prior art discussed above does not show a design that does not rely on body bolting or fasteners of any kind to retain the valve stem within the pressure area of a valve with a trunnion mounted rotary element. Those of skill in the art will appreciate the present invention that addresses the above needs and other significant needs, the solution to which are discussed hereinafter.